Apparatus for the treatment of pulps



June 14, 1966 D. WESTON 3,255,999

APPARATUS FOR THE TREATMENT OF PULPS Original Filed Jan. 21, 1959 //vl/EA/TOK 94 W0 M55 70 ByWfff flrraemevs United States Patent 4 Claims.(Cl. 259-2) This application is a division of US. application Serial No.788,175, tiled January 21, 1959, now abandoned.

This invention relates to an apparatus for the application of reagentsto finely divided particulate materials While the latter are suspendedin a liquid pulp. More particularly, in its primary application theinvention relates to the application of reagent to such materials inorder to prepare the latter for a subsequent flotation step in which oneor more constituents of the material are to be concentrated.

Certain materials are generally regarded as refractory to flotation.These include such materials as manganese oxides, iron oxides, oxidizedsulphides of lead, copper and Zinc, and many others. Various attemptshave been made to concentrate such materials by flotation and ingeneral, although concentration can be achieved in most cases, reagentconsumption is high and recoveries and grades of concentrate arecomparatively low, so that economically acceptable operation of suchprocesses has in general not been satisfactory. One feature of many suchmaterials is that in many cases in addition to naturally occurringslimes, reduction of the material to an appropriate stage of mineralliberation involves the production of a considerable additional quantityof slimes, which it' has heretofore been necessary to eliminate priortoflotation, resulting in a substantial amount of the head value of thematerial being lost with the slimes which are eliminated.

It has recently been shown that in at least some instances it ispossible to float slimes through the use of exorbitantly highconcentrations of reagent or through the use of certain special reagentswith a very long period of conditioning. Neither system can be regardedas economically satisfactory as long conditioning times are costly bothin power consumption and in capital cost and maintenance cost of theplant involved. Where flotation of slimes is achieved by the use ofexorbitantly high reagent concentrations, the cost of the reagentconsumed is frequently higher than the worth of the values recoveredfrom the slimes.

The present invention provides a means for activating refractorymaterials, and in particular materials associated with slimes in a muchshorter period of time than has heretofore been possible, and withgreatly reduced reagent consumption. The invention, while leading tooutstanding benefits in relation to refractory ores and slimes, isgenerally applicable to all types of material and is capable ofproducing reduction of reagent consumption and/ or increases of recoveryand/ or grade in almost all cases.

Broadly speaking, the invention is based upon the novel conception thatreagent. may successfully and rapidly be applied to refractoryparticles, including slimes, by firstly having the reagent in finelysubdivided form in a physical condition in which at least during itsperiod of application it is capable of existing as a liquid phaseseparate from the liquid of the pulp, and secondly by the maintenance insuch particles of reagent at least during the period of applicationthereof of a level of energy in re- 3,255,999 Patented June 14, 1966going concept is put into practice by suspending the particulatematerial to be treated in a first liquid to form a pulp, andestablishing and maintaining within the said pulp a localized zone ofconcentrated reagent activity into which the reagent is fed as a finelydivided mechanical dispersion in the form of a second liquid which isimmiscible with said first liquid at least to the extent necessary tomaintain the droplets of reagent as a sepical dispersion of the reagent.

lation to the particulate material being treated suflicient to overridethe existing interaction of forces at the solid liquid interface betweenthe particles of material and I the pulp liquid.

Broadly speaking according to the invention, the forearate phase for theconditioning period, while the pulp is progressively passed through saidzone.

The level of available energy possessed by the particles of reagent maybe influenced in many difierentways. To begin with, the formation of afinely divided mechanical dispersion creates available energy at thesurface of the reagent particles which is of a higher order of potentialthe smaller the particles. This energy is in very many cases sufficientto overcome the existing forces of the solid liquid interface of theparticles of material. Where a higher level of available energy isrequired, this may be supplied within the zone of concentrated reagentactivity by elevation of temperature, pressure, or both, by raising thekinetic energy of the pulp within said zone by agitation or the creationof conditions of elevated or extreme turbulence, by the application ofsonic, supersonic or ultrasonic vibration, or where applicable, theapplication of static or alternating electrostatic or electromagneticfields. Alternatively to the foregoing or in conjunction therewith, theavailable energy of the reagent particles may be increased byintroducing the reagent as a water soluble substance dissolved in awater insoluble vehicle. In this case, as the reagent droplets becomemixed with the liquid of the pulp the water soluble reagent within thedroplets will seek to distribute itself on either side of the interfaceboundary; and there will thus be established surrounding each droplet azone of high reagent concentration during the period of conditioning,the concentration of reagent within such zone being sufiicient toovercome the forces acting at the solid liquid interface of particles tobe treated.

In order for the droplets of the reagent dispersion to be maintained asa separate'liquid phase during passage through the zone of concentratedreagent activity it is not necessary that the reagent droplets beentirely immiscible with the pulp liquid, it is only necessary thatthere be sufficient immiscibility that a phase boundary between the twoliquids is preserved for a final period which corresponds at least tothe time it takes: the reagent particle to pass through the zone. Thismay in some cases be extremely short, i.e. of the order of a fewmilliseconds. In the absence of a conventional term to express therequired degree of immiscibility, the required degree is referred toherein as being effective immiscibility, the reagent being described aseffectively immiscible with the pulp liquid.

It will be appreciated that as in all operations which relate to thetreatment of naturally occurring materials the treatment of anyparticular material will involve an appropriate selection of thereagents and the conditions of application thereof in order to securethe best and most economical results.

Various ways are available in which to form a mechan- One suitablemethod is to form such dispersion in a stream of air or other gas inertto the proposed conditioning operation by means of a fog nozzle. Theresulting air dispersion may then be introduced to the zone ofconcentrated reagent activity in the pulp either in the body of thepulp, or to the air intake of a flotation machine or in various otherways, a number of which will be hereinafter described. Instead offorming the dispersion in a stream of air or inert gas, it may be founddesirable to introduce the dispersion in a stream of soluble gas such ascarbon dioxide. Alternatively, the reagent may be introduced by means ofa steam line either by forming a mechanical suspension of droplets inthe steam itself where the reagent is substantially insoluble in steamor does not vaporize therein, or in the case where the reagent issoluble or unstable in steam or vaporizes at the temperatures of thesteam line, simply by feeding the reagent in metered quantities to thesteam so that as the steam condenses within the zone of concentratedreagent activity the reagent is left as a mechanical dispersion in thepulp as it condenses. It will be appreciated that introduction of thereagent in a steam line will produce a very high degree of kineticenergy in the zone of concentrated reagent activity owing to the shockwaves produced by the condensing steam.

Instead of using air or gas or vapor as a vehicle for the dispersion ofreagent, such dispersion may be formed utilizing a liquid vehicle, thelatter being either a liquid readily miscible with the liquid of thepulp, water, or pulp liquid which is recycled, e.g., from a filtrationor other dewatering stage of the process involved. Such dispersion canbe formed by means of high speed mechanical impellers placed in the feedline or by forcing concurrent streams of the reagent and vehicle throughappropriately designed mixing chambers of conventional construction. Itis important particularly where liquid vehicles are used that theformation of the dispersion take place as closely as possible to thepoint of introduction of the dispersion to the zone of concentratedreagent activity in the pulp, so that the surface energy created on thedispersed droplets has as little time as possible to dissipate beforeintroduction thereto. The use of emulsifying agents and other surfaceactive agents to promote dispersion is to be avoided as the latter tendto maintain intact the face boundary between the dispersed reagent andthe vehicle with the consequence that the surface energy produced by thecreation of the dispersion is in effect neutralized and is not availableto assist in the displacement of the solid liquid interface at thesurface of the particles of material. In order to distinguish the typeof dispersions preferred in the practice of the present invention fromstabilized dispersions such as colloids and emulsions which have beenstabilized with surface active agents, I refer herein to suchdispersions as are preferred in the practice of the invention as dynamicdispersions.

A preferred manner of employing the present invention embodies theformation of the zone of concentration of reagent activity within one ormore mixing chambers placed in a line through which the pulp is fed byappropriate means. A preferred application of energy to the said zone inthis instance is through the use of a concentration of ultrasonic energyprovided by ringing a number of supersonic generators around the outsideof the mixing chamber as will hereinafter be described. In this instancethe feed lines for the dispersion of reagent will enter the mixingchamber at the throat thereof, and the application of ultrasonic energymay be made just prior to or just after the introduction of the reagentdispersion or both. A particular advantage of this embodiment of theinvention resides in the fact that the use of ultrasonic frequencieswithin the relatively small enclosed space of the mixing chamber tendsto disassociate particles of slime from larger particles of particulatematerial to which they may be adhering, and thus said particles becomefreed for independent application to them of the reagent.

The invention now having been described in some of its broader aspects,a better understanding of its application may be had by reference to thefollowing detailed explanation of its application by means both ofconventional apparatus and of novel apparatus particularly adapted tocarry it out. The application of the invention will be described inconjunction with the accompanying drawing wherein:

FIG. 1 is a diagrammatic view of suitable apparatus for the formation ofthe zone of concentrated reagent activity within a mixing chamber placedin a line through which the pulp is flowing;

FIG. 2 is a diagrammatic illustration of a specially designed mixingchamber which is adapted to provide for application of supersonic orother energy to the material both before and after introduction of thereagent.

In FIGS. 1 and 2 are illustrated novel alternative forms of apparatuswhich are particularly adapted to carry out the method of the presentinvention.

Referring particularly to FIG. 1, the mixing chamber is connected bymeans of a rubber flange 81 to a line 82 through which is being fed apulp of the material to be treated preferably at a high solids liquidratio (i.e.

up to 70-75% solids). The mixing chamber 80 is also connected todischarge line 33 through the rubber flange 84. A plurality of nozzles85 supplied by lines 86 and 87 are directed into the interior of themixing chamber 80 adjacent the inlet end thereof while the body of themixing chamber 80 is surrounded with the generators 88 which consist ofa plruality of ultrasonic vibration generators, or which mayalternatively be generators of any other selected form of high energyoscillation. In operation, the incoming reagent dispersion from nozzles85 is intimately mixed and dispersed in the pulp coming into chamber 80from line 82. As this mixing action is taking place, the energy from thegenerator 88 will be assisting both the mixing action and by the releaseof energy within the pulp, the association of the reagent with theparticles of mineral. A typical application for an apparatus of the typeillustrated in FIG. .1 is that of the treatment of manganese or hematiteore from a tailings dam with tall oil for subsequent flotation.

In FIG. 2, a special unit is illustrated adapted to be connected byrubber flanges 9t and 91 in a line carrying pulp of a material to betreated. The device illustrated has an-inlet duct 92 leading to aventuri throat 93, which in turn leads into the expansion chamber 94.Ultrasonic generators 95 are situated around the inlet duct 92 todisassociate slimes within the pulp from larger particles to which theseslimes may be adhering. A plurality of nozzles 96 are directed into thethroat of the venturi 93, these nozzles 96 being supplied by the twosupply lines 97 and 98. The zone of concentrated reagent activity isformed within the expansion chamber 94 where the high turbulence notonly produces efi'lcient mixing of the reagent dispersion with the pulp,but also builds up high electrostatic forces and mechanical forces dueto the friction produced within the pulp. The latter action may beaugmented by means of pulse generators 99 placed around the expansionchamber generating as may be appropriate either ultrasonic, highfrequency electrostatic or electromagnetic pulses. In many cases steammay be used as the vehicle for the reagent dispersion adding to theavailable energy in the zone of concentrated reagent activity both byelevating the temperature and in the production of shock waves as itcondenses.

In addition to its use which has already been described in some detailfor purposes of conditioning refractory materials for flotationoperations, the method of the present invention lends itself to avariety of other applications. For instance, in the conditioning ofmagnetite for wet magnetic separation, the reagent sodium silicate maybe introduced through line 96 as a dispersion either in air or in water,and the application of sodium silicate to the particles of the pulpwhich takes place in the zone of concentrated reagent activity which ispresent in the expansion chamber 94 produces a complete dispersion ofthe magnetite allowing each particle of the pulp to move independentlyunder the influence of the magnetic field in the subsequent magneticseparation step.

With suitable modifications to enable the handling of corrosivematerials, an apparatus such as that illustrated in FIG. 2 may be usedin the employment of the process of the invention in order to carry outa leaching operation.

As is well known, conventional leaching involves the use of greatvolumes of liquid and long hold-up times. The reason for this is that inorder to achieve adequate wetting of the material to be leached arelatively large volume of water is considered necessary. In order tomaintain reagent costs Within economic limits, the concentration ofreagent in the leaching baths is comparatively low. As a result, thesolution time of the soluble constituents of the material being leachedis correspondingly long. By utilizing the method of the presentinvention, it is possible to disperse a small volume of relativelyconcentrated reagent throughout a mass of relatively dense pulp so thatthe reagent is available throughout the mass at a relatively highconcentration. It is further possible by the application of externalenergy such as ultrasonic vibration to overcome the air solid and airliquid interfaces which are the result of imperfect wetting with theeffect that not only is the leaching time reduced to the point where thesolution of the materials to be leached can take place almostimmediately, but this result is achieved with a minimum amount ofdilution so that the total volume of solution resulting from the leachis very materially reduced and the values in such solutions are verymaterially more concentrated than is presently possible by conventionalmethods.

It will be appreciated from the foregoing that the present inventionprovides a novel, effective apparatus for the application of reagent toparticulate materials where the latter are in the form of a pulp. Itwill further be appreciated that the invention is one of broadapplication and that it is not to be construed as being limited merelyto the specific applications which have been given herein by way ofillustration.

What is claimed is:

1. An apparatus for the application of reagents to particulte minerals,said particulate minerals being in the form of a slurry or pulp, saidapparatus comprising a hollow casing providing a mixing chamber for saidslurry or pulp, an inlet port communicating with said mixing chamber bymeans of which said slurry or pulp enters said mixing chamber, an outletport communicating with said mixing chamber by means of which saidslurry or pulp is discharged from said mixing chamber, flexibleconnection means associated with said inlet and outlet ports wherebysaid casing may be connected in a fluid line to vibrate substantiallyindependently of said line, at least one nozzle mounted to said casingforward of said inlet port with the discharge end of the nozzle directedinto the mixing chamber of said casing, a first and second supply meansconnected to said nozzle to controllably supply two separate reagentcomponents to said nozzle, said nozzle being adapted in operation toform and project into the mixing chamber of said casing a dynamicdispersion of one of said reagent components in the other and establisha zone of concentrated reagent activity in said mixing chamber, andmeans mounted at the exterior of said casing forward of said nozzle andsurrounding the mixing chamber confining said zone of reagent activityfor applying high frequency oscillation to said zone of concentratedreagent activity established by the dynamic dispersion projected by saidnozzle.

2. The apparatus of claim 1, including means mounted on the exterior ofsaid casing between the inlet port and said nozzle for applyingultrasonic vibration to the particulate minerals flowing past saidnozzle.

3. The apparatus of claim 1, wherein the hollow casing is formed toprovide a venturi forward of said inlet port which leads into anexpansion chamber comprising said mixing chamber, wherein said at leastone nozzle forward of said inlet port is directed through said casing atthe venturi thereof into said expansion chamber whereby to establish aconcentrated zone of reagent activity within said expansion chamberforward of said nozzle, and wherein the high frequency oscillation meansis mounted about the expansion chamber containing said zone ofconcentrated reagent activity.

4. The apparatus of claim 3 including means mounted on the exterior ofsaid casing between the inlet port and the venturi for applyingultrasonic vibration to the particular mineral flowing past said nozzle.

References Cited by the Examiner UNITED STATES PATENTS Westbrook 2592WALTER A. SCHEEL, Primary Examiner. JOHN M. BELL, Assistant Examiner.

1. AN APPARATUS FOR THE APPLICATION OF REAGENTS TO PARTICULATE MINERALS,SAID PARTICULATE MINERALS BEING IN THE FORM OF A SLURRY OR PULP, SAIDAPPARATUS COMPRISING A HOLLOW CASING PROVIDING A MIXING CHAMBER FOR SAIDSLURRY OR PULP, AN INLET PORT COMMUNICATING WITH SAID MIXING CHAMBER BYMEANS OF WHICH IS SLURRY OR PULP ENTERS SAID MIXING CHAMBER, AN OUTLETPORT COMMUNICATING WITH SAID MIXING CHAMBER BY MEANS OF WHICH SAIDSLURRY OR PULP IS DISCHARGED FROM SAID MIXING CHAMBER, FLEXIBLECONNECTION MEANS ASSOCIATED WITH SAID INLET AND OUTLET PORTS WHEREBYSAID CASING MAY BE CONNECTED IN A FLUID LINE TO VIBRATE SUBSTANTIALLYINDEPENDENTLY OF SAID LINE, AT LEAST ONE NOZZLE MOUNTED TO SAID CASINGFORWARD OF SAID INLET PORT WITH THE DISCHARGE END OF THE NOZZLE DIRECTEDINTO THE MIXING CHAMBER OF SAID CASING, A FIRST AND SECOND SUPPLY MEANSCONNECTED TO SAID NOZZLE TO CONTROLLABLY SUPPLY TWO SEPARATE REAGENTCOMPONENTS TO SAID NOZZLE, SAID NOZZLE BEING ADAPTED IN OPERATION TOFORM AND PROJECT INTO THE MIXING CHAMBER OF SAID CASING A DYNAMICDISPERSION OF ONE OF SAID REAGENT COMPONENTS IN THE OTHER AND ESTABLISHA ZONE OF CONCENTRATED REAGENT ACTIVITY IN SAID MIXING CHAMBER,